H. Rubens and E. F. Nichols
Phys. Rev. (Series I) 5, 152 (1897) - Published 1 September, 1897
N. Ernest Dorsey
Phys. Rev. (Series I) 5, 170 (1897) - Published 1 September, 1897
Robert L. Litch
Phys. Rev. (Series I) 5, 182 (1897) - Published 1 September, 1897